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Supply-demand balance (MWh)
======

*indexed by asset, data type (Demand or Production), energy, node, technology and test case*

### Description

This KPI returns the volumes of energy consumed and produced over the entire simulation for every energy, node, asset, and technology of a given context (except for CO2 energies: see [specific KPI](co2_sdb.md)).

The results indicated in this KPI are directly those of the optimization problem.
If an asset produces, it will appear in the *Production* tag of the "Data type" index.

For example, a storage asset may appear in both the *Production* and *Demand* tags, as it
consumes energy to store it and produces energy during its life cycle.

<blockquote class="custom-hint">
  <h4>Modelling hint</h4>

  Note that Voluntary Load Curtailment, which represents consumption curtailment, and Loss of
  Load, which represents failure, are modelled as production assets. They will therefore appear in the *Production* tag.
</blockquote>

This KPI is particularly interesting to understand the equilibrium between the national production and the national demand over a node for a given energy.

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### Calculation

The equations below are valid for any realization and are therefore implicitly indexed by test case. Index *Technology* is directly deduced from the asset.

#### Production

Let be $x_{a, e, n}$ the value returned by the data type *Production* for a given asset $a$, energy $e$ and node $n$.
We can then express $x_{a, e, n}$ as:

$$
x_{a, e, n} = \frac{1}{N_h} * \sum_{\text{timestep } t} p_{a, e, n}(t)
$$

#### Consumption

Let be $x_{a, e, n}$ the value returned by the data type *Consumption* for a given asset $a$, energy $e$ and node $n$.
We can then express $x_{a, e, n}$ as:

$$
x_{a, e, n} = \frac{1}{N_h} * \sum_{\text{timestep } t} c_{a, e, n}(t)
$$

*Global variables and parameters notations definitions can be consulted [here](../notations.md).*